This application relates to an improvement in discharge valve structure for a scroll compressor wherein return passages to force a valve to a closed position upon reverse rotation of the scroll compressor are optimized.
Scroll compressors are becoming widely utilized in refrigerant compression applications. As is known, a scroll compressor includes a first scroll member having a base and a generally spiral wrap extending from the base. A second scroll member has a base and a generally spiral wrap extending from its base. The two wraps interfit to define compression chambers. The second scroll member orbits relative to the first scroll member. As the orbiting occurs the size of the compression chamber decreases, and gas is compressed and forced towards a central portion of the two wraps. A discharge port extends through the base of the first scroll member at a central location.
Scroll compressors may sometimes experience reverse rotation at shutdown. At shutdown, compressed fluid which has recently been compressed by the scroll members may sometimes move back through the discharge port and into the compression chambers between the two scroll wraps. When this occurs, the orbiting scroll member can be forced to orbit in a reverse direction to that which is normally proper for operation of the scroll compressor. This so-called reverse rotation creates undesirable noise.
Attempts have been made to reduce the occurrence of this reverse rotation at shutdown. One specific attempt involves the use of a discharge check valve which seals the discharge port.
To this end, the check valve is allowed to float within a valve chamber. Gas is communicated to discharge passages radially outward of this valve. The valve sits against the valve seat, and is held upwardly against the valve seat during normal operation. Discharge pressure fluid is communicated to a rear face of the valve; however, during forward operation the flow from the compressed gas holds the valve against the valve seat.
However, when the compressor is stopped, the discharge pressure gas passes through the passages to the rear face of the floating valve. The floating valve is then forced back to close the discharge port.
The known return passages have not been operational as quickly as would be desired. In general, the passages have included straight passages which are parallel to the axis of the orbiting scroll member. Other proposed valves have used the discharge passages to provide the return passage function. This has resulted in some restriction in flow, and thus a delay in the valve moving to the closed position at shutdown.
Other structures have the valve extending outwardly radially beyond the surface of the valve stop. This, however, results in undesirable valve flutter noises during normal operation.
In general, the return passage structure which has been utilized in the prior art has some undesirable characteristics. The present invention improves upon the return passage structure.